Temperature gradient models of steel-concrete composite girder based on long-term monitoring data

Although thermal effects of composite girder bridges are considered in current specifications from many countries, the recommended temperature gradient models are not appropriate enough for steel-concrete girders. Moreover, these temperature gradients are not suitable for long-lasting bridges with over 100 years design working life. To further investigate temperature gradient models for composite girder bridges, long-term monitoring was carried out on a composite girder test model. Based on the 6-year temperature data set, the temperature distribution patterns of composite girder under typical weather conditions were investigated firstly, then the profiles and standard values of the most critical temperature gradient are given through statistical analysis. Specifically, the standard values for different design return periods are calculated to meet the requirements of ordinary bridges and long-lasting bridges. The thermal stress verifications of proposed models are conducted in the last by comparing the thermal stresses induced by the temperature gradient in current specifications, which proves that the proposed models could better represent real thermal loads for the test girder model.